Hydraulic power-transmitting apparatus



Apri1 8, 1930. R. K. PIERSON ET AL HYDRAULIC POWER TRAN SMITTING APPARATUS Filed June 13, 1929 Patented dpr, 8, 193m REGINALD KIR$HAW PTERSON AND THOMAS SMITH. DUNUMN, U1! WEETMINfiTEM, ENGLAND, ASSIGNORS T0 VICKERS LIMITED, 015 WEEFTMINSTER, ENG-LAND, A.

BRITISH COMPANY HYDRAULIC POWER-TEAN$MITTTNG MPTWfi Application filed June 13, 19%, Serial u'ojavaera, and in Great Britain March it), that.

This invention relates to hydraulic power transmitting apparatus cit-the kind in which liquid is forced by a hand-operated pump into one or more motors for actuating the desired mechanism which, for example, may be the brakes of an aeroplane under-carriage or other wheeled vehicle. In certain types of such apparatus the pump is of the piston or plunger type operated by a hand lever and the liquid flows to the motor or motors past a delivery valve which is lifted from its seat by the liquid during the pumping stroke and is returned to its'seat by the back pressure or the liquid during the suction stroke. The

' liquid pressure therefore cannot be reduced to enable the motor or motors to'return to or towards the original position without the introduction of a release valve or other control device additional to the pump hand lever and separately controlled by the operator, which is disadvantageous particularly in the case of brakes where it is desirable to have precise control of the braking force exerted.

According to the present invention means is provided whereby, when a predetermined degree of pressure of the liquid has been exceeded, the aforesaid delivery valve is unseated, so that there is then uninterrupted liquid communication between the pump and the motor or motors with theresult that pre cise control of the latter can be obtained not only towards the maximum position, but also towards the minimum or original positip'n up to a point at which the liquid pressure is reduced to the predetermined degree at which the delivery valve returns to its seat. To release the pressure completely, we may provide means whereby movement of the aforesaid hand lever beyond its normal maximum position on the suction stroke, moves the delivery valve mechanically from its seat so as to establish free communication between the motor or motors and the usual liquid supply reservoir open to the atmosphere. We may also provide means operated by the said hand lever for mechanically returning the delivery valve to its seat at the end of each pumping stroke so that the motor or motors can, if desired, be allowed to remain in the positionto which it or they have been moved, until the hand lever is again operated. I

In order that the invention may be clearly understood and readily carried into efiect it will now be described more fully with reference to the accompanying drawing, in

which Fig. 1 is a sectional view of a pump suitable for transmitting power hydraulically to the brakes or an aeroplane under-carriage, and Fig. 2 is a plan view of the guide plate.

Tn the form of the invention illustrated the hand lever 1 is mounted in the aeroplane cockpit in a position for ready actuation by the pilot, being pivoted at 2 and having a rearwardly extending arm 3 connected to the plunger 4 of the pump by such means as a transverse slot 5 embracing the spherically formed end 6 of the arm 3. The plunger 4 works in a cylinder 7 communicating with a liquid reservoir 8 open to the atmosphere and also with a small chamber 9 having a seat for receiving an outwardly opening valve 10 which, as indicated, may conveniently be or the ball type. The plunger 4 serves, during the early part of its downward pumping stroke, to cut 0d communication between the cylinder 7 and the reservoir 8 so that a suction valve is unnecessary. The outlet pipe 11 from the small chamber 9 may communicate by means of pipes with small cylinders containing rams which operate the brakes of the under-carriage wheels, which brakes may conveniently be out the servo-motor type of any known or suitable construction. The delivery valve 10 has'a stem 12 which passes out to the atmosphere, it necessary through a gland, so that the valve is of the unbalanced type. v llt is normallylield on its seat by a helical compression spring 13 of such strength that when the pressure generated by the ump exceeds a predetermined degree the va vs 10 is moved off its seat and remains ofl' so long as that particular degree of pressure is maintained or exceeded. lit usually requires a few strokes of the plunger 4 for the said degree of pressure to be reached and during these strokes the liquid passing from the cylinder 7 to the ram cylinders appertaining to the brakes merely serves to take up the usual runreach and then exceed the degree at which the delivery valve is held ofi? its seat. Under these conditions there are uninterrupted columns of liquid between the pump plunger 4 and the plungers of thebrakes so that the pilot can feel the brakes, that is to say he can tell what braking pressure he is exerting in a similar manner to that which occurs with the mechanically operated brakes of motorpropelled vehicles and he can increase or decrease the braking pressure at will, the limit of decrease by normal manipulation of the pump hand lever 1 being determined by the minimum pressure at which the delivery valve 10 is maintained off its seat. When the pres} sure falls below this point the valvelO acts as an ordinary non-return valve, and in order that the pressure maybe completely relieved when required so as to allow the brakes to return to their inoperative position, a link 14, hinged to an arm 15 of the lever 1, is adapted to co-operate with a 'stop 16 on the valve stem 12 to unseat the Valve 10 against the resistance of its spring 13 when forward movement is given to the hand lever 1 beyond the position shown which is the end of its normal suction stroke. To prevent this further movement of the lever 1 taking place inadvertently during the pumping operations, the lever is arranged to work in a slot 17 in an arcuate plate, shown separately in plan view,

which has a small portion 18 at its forward end ofiF-set-slightly with respect to the main portion so that it becomes necessary to move the lever 1 sideways in order to enter the portion 18' for lifting the valve 10 from its seat. Sufiicient play is provided around the I pivotal connections to permit such lateral movement. 1

The link 14 may also co-operate with another stop 19 on the valve stem 12 when'the rearward or pumping movement of the lever 1 is reached so as to bring the valve 10 mechanically on to. its seat, thus maintaining the brakes in the position to which they have been brought by the pumping action. As the pressure on both sides of the valve 10 may be very high there may be a tendency for the valve to leave its seat owing to the fact that it is of the unbalanced type. This tendency can be overcome by moving the hand lever 1 sharply in the forward direction after the valve has been seated mechanically, thus causing the pressure on the larger area of the valve to fall quickly so that the valve is then maintained on its seat by the pressure obtaining in the pipe 11.

The motor, of any suitable cated diagrammatically at 20.

What we claim and desire to secure by Lettype, is indi- .ters Patent of the United States is 1. Hydraulic power transmitting apparatus comprising in combination a hand-operated plunger pump, a liquid-pressure-actuated motor, a pipe connecting said pump and said motor, an unbalanced non-return delivery valve in said pipe and means for positively maintaining said delivery valve in closed position when said pump plunger is at the end of its delivery stroke.

2. Hydraulic power transmitting apparatus comprising in combination a hand-operated plunger pump, a liquid-pressure-actuated motor, a pipe connecting said pump and said motor, an unbalanced non-return de livery valve in said pipe and means for me chanically opening said delivery valve when said pump plunger is moved beyond the end of its normal suction stroke.

3. Hydraulic power transmitting apparatus as in claim 2, provided with means including a slotted member cooperating with the pump handle, to prevent unintentional movement of said pump plunger beyond the end of its normal suction stroke.

. 4. Hydraulic power transmitting apparatus comprising in combination a hand-operated plunger pump, a liquid-pressure-actuated motor. a pipe connecting said pump and said motor, an unbalanced non-return delivery valve in said pipe, a stem to said valve, at least one stop fitted on said stem, a hand .lever for reciprocating said pump plunger, 

